1. Technical Field
The present invention relates to a chemical mechanical polishing (CMP) apparatus that is capable of polishing a wafer by a chemical mechanical polishing (CMP) process, and in particular relates to a CMP apparatus that is capable of polishing an edge section of a boundary between a front surface and a circumference surface of a disc-shaped wafer.
2. Related Art
Currently, a CMP apparatus is utilized in a manufacture of a semiconductor device. Such CMP apparatus includes a turn table, on which a CMP pad is detachably mounted. A semiconductor wafer, which is in manufacture of semiconductor devices therein and serves as a workpiece, is pressed against a front surface of a CMP pad that is actuated to be rotated together with the turn table.
In such case, the semiconductor wafer reciprocates along a radial direction of the CMP pad. Moreover, a slurry is supplied onto the front surface of the CMP pad. Further, the front surface of the CMP pad is dressed with a dresser, which also reciprocates along a radial direction.
In the manufacturing process of semiconductor devices, film depositions and micro-fabrications are repeated. In depositions of layer films, layer films are also formed on inclined sections and/or round sections in vicinity of a circumference section of a semiconductor wafer. Improvements in clamp rings employed in the deposition process achieve an improvement in a prevention for depositions of films onto a side surface and/or a back surface of a semiconductor wafer.
However, the circumference portion of the semiconductor wafer is in contact with a cassette for semiconductor wafers, causing an adhesion of a contaminant due to creations of contaminants in the contacting spots. When layer films are formed at such contacting spots, the contaminants causes a generation of flaking off.
Thus, a countermeasure for the above-described flaking-off is required in the manufacturing process for the semiconductor devices. To solve the problem, as shown in FIG. 6, an edge polishing apparatus 10 for polishing an edge of a circumference section of a semiconductor wafer W is proposed (see, for example, Japanese Laid-Open Patent No. 2001-345,298).
However, the present inventor has recognized that in the edge polishing apparatus 10 described in the above-described Japanese Laid-Open Patent No. 2001-345,298, a polishing pad 12 supported by a turn table 11 is continuously in contact with the circumference section of the semiconductor wafer W.
Thus, it is constitutively difficult to perform a dressing the polishing pad 12 that is in an operation for polishing the semiconductor wafer W, simultaneously with the polishing.
Therefore, the surface of the polishing pad 12 may be crushed by the pressure, or a clogging with a polishing scum may be caused. Such case causes an unstable rate of an edge polishing, which is an intended purpose in the CMP process, causing an impossible removal of the layer film from the circumference section of the semiconductor wafer W.
In order to prevent such problem, for example, it is considered that an in creased processing time with the edge polishing apparatus 10 is employed. However, this also causes a decreased productivity of the semiconductor devices, causing increased wear and tear in the edge polishing apparatus.